COMMITMENTS AND CONTINGENCIES - Narrative (Details) $ in Millions	12 Months Ended
	Jun. 30, 2018 USD ($) Facility	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)
Lessee, Lease, Description [Line Items]
Number of fully-permitted facilities | Facility	2
Number of processing and treatment facilities | Facility	1
Rent expense | $	$ 2.0	$ 1.5	$ 0.9
Performance bonds outstanding covering financial assurance | $	$ 0.7
Minimum
Lessee, Lease, Description [Line Items]
Option to renew lease, term	1 year
Maximum
Lessee, Lease, Description [Line Items]
Option to renew lease, term	5 years